1. Field of the Invention
The present invention relates generally to a gas turbine engine, and more specifically to a turbine rotor blade with multiple zone cooling based on airfoil gas side pressure and heat load.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In a gas turbine engine, such as a large frame heavy-duty industrial gas turbine (IGT) engine, a hot gas stream generated in a combustor is passed through a turbine to produce mechanical work. The turbine includes one or more rows or stages of stator vanes and rotor blades that react with the hot gas stream in a progressively decreasing temperature. The efficiency of the turbine—and therefore the engine—can be increased by passing a higher temperature gas stream into the turbine. However, the turbine inlet temperature is limited to the material properties of the turbine, especially the first stage vanes and blades, and an amount of cooling capability for these first stage airfoils.
The first stage rotor blade and stator vanes are exposed to the highest gas stream temperatures, with the temperature gradually decreasing as the gas stream passes through the turbine stages. The first and second stage airfoils (blades and vanes) must be cooled by passing cooling air through internal cooling passages and discharging the cooling air through film cooling holes to provide a blanket layer of cooling air to protect the hot metal surface from the hot gas stream.
A single turbine rotor blade with be exposed to different gas flow temperatures and pressures around the surfaces. For example, the leading edge is exposed to the highest gas flow pressures and temperatures. The airfoil trailing edge on the suction side is exposed to the lowest gas flow pressures. In order to cool the blade more efficiency and to prevent certain surfaces from over-heating, tailoring the cooling throughout the blade is needed. Hot spots cause erosion of the blade surface that decreases turbine efficiency and shortens the useful life of the blade. Excessive cooling air flow will decrease engine efficiency from the extra work done on compressing the cooling air that is not needed for cooling.